Upcycling of Battery Waste for Enhanced Photocatalytic Hydrogen Production

The valorization of spent battery components into high‐performance functional materials presents a promising avenue for sustainable resource management. In this study, we successfully recovered and repurposed materials from spent alkaline batteries, separating them into carbon‐based cathode powders (black fraction) and zinc (Zn)‐based anode powders (white fraction). While the cathode material consists primarily of carbon and oxygen, the anode material comprises Zn‐based compounds, including zinc oxide (ZnO). We demonstrate that simple calcination treatment at 80°C transforms the recovered Zn‐based powder (DW_V‐80) into a highly efficient photocatalyst. X‐ray diffraction analysis reveals the optimized material as a crystalline composite of ZnO and zinc nitrate hydroxide hydrate (Zn 5 (NO 3 ) 2 (OH) 8 ·2H 2 O), exhibiting superior photocatalytic H 2 evolution activity, producing ≈350 μmol of H 2 in 5 h. In contrast, the carbon‐based materials showed negligible photocatalytic activity. The enhanced performance of DW_V‐80 is attributed to the synergistic effect between the two crystalline phases and optimal concentrations of structural defects, such as oxygen vacancies, induced by mild thermal treatment. This work highlights a simple yet effective strategy to upcycle waste battery materials into valuable photocatalysts for solar fuel production.